Computing devices, such as notebook computers, personal data assistants (PDAs), and mobile handsets, have user interface devices, which are also known as human interface device (HID). One user interface device that has become more common is a touch-sensor pad. A basic notebook touch-sensor pad emulates the function of a personal computer (PC) mouse. A touch-sensor pad is typically embedded into a PC notebook for built-in portability. A touch-sensor pad replicates mouse x/y movement by using two defined axes which contain a collection of sensor elements that detect the position of a conductive object, such as finger. Mouse right/left button clicks can be replicated by two mechanical buttons, located in the vicinity of the touchpad, or by tapping commands on the touch-sensor pad itself. The touch-sensor pad provides a user interface device for performing such functions as positioning a cursor, or selecting an item on a display. These touch-sensor pads can include multi-dimensional sensor arrays. The sensor array may be one dimensional, detecting movement in one axis. The sensor array may also be two dimensional, detecting movements in two axes.
FIG. 1 illustrates an example of a conventional slider structure 100 connect to ten conductive traces 102. Each trace 102 may be connected between a conductive line and a ground. The conductive line is typically coupled to a sensing pin. The ground is typically coupled to a finger of person. By being in contact or in proximity on a particular portion of the slider structure 100, the capacitance between the conductive lines and ground varies and can be detected. By sensing the capacitance variation of each trace 102, the position of the changing capacitance can be pinpointed. For example, a stylus or a user's finger in proximity or in contact to the slider structure 100 generates signals 104 using the traces 102. A stylus or a user's finger in proximity or in contact to the slider structure 100 at trace number 4 may generate a capacitance variation differential of, for example, 5 units. Adjacent traces number 3 and number 5 may respectively generate a capacitance variation differential of, for example, 2 and 3 units. The detected position of the finger or stylus (i.e., centroid position) may be detected using a complex formula.